4 modbus communication protocol, Slave address setting, Data communication format – Ronan X11CA User Manual
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Rev 2.0 : X11CA-IM MASTER MODULE
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4 MODBUS COMMUNICATION PROTOCOL
4.1 Slave Address Setting
The Slave Address switch (SW1 or SW3, depending on the revision of the PCB) on
the X11CA-IM Module sets the Slave Address of the X11CA-IM Master Module
for MODBUS RTU communication as shown below.
Slave
address
SW1-1
SW1-2
SW1-3
SW1-4
1
OFF
OFF
OFF
OFF
2
ON
OFF
OFF
OFF
3
OFF
ON
OFF
OFF
4
ON
ON
OFF
OFF
5
OFF
OFF
ON
OFF
6
ON
OFF
ON
OFF
7
OFF
ON
ON
OFF
8
ON
ON
ON
OFF
9
OFF
OFF
OFF
ON
10
ON
OFF
OFF
ON
11
OFF
ON
OFF
ON
12
ON
ON
OFF
ON
13
OFF
OFF
ON
ON
14
ON
OFF
ON
ON
15
OFF
ON
ON
ON
16
ON
ON
ON
ON
Table 4-1 Setting Modbus Slave Address
4.2 Data Communication Format
The data format for Modbus communication is 19200, no parity, 8 bit and 1 stop
bit.
4.3 Modbus RTU Protocol Function 3: Read the Holding Registers
To read the binary contents of the holding registers on the X11CA-IM from a host
device, use Modbus RTU Protocol function 3.
Query
The query message specifies the starting register and the quantity of registers
to be read. Registers are addressed starting at zero: registers 1-16 are addressed
as 0-15.